As it is well known, protection in radio transmission is an important task to be taken into account. Protection in the context of the present invention refers to any action or means employed in order to ensure a non-faulty transmission or to reduce the effects of an eventual fault. In general, when a fault is detected in a link during transmission, the transmission is maintained active by putting a second link, the protection link, in operation. Various types of protection in radio environment are known. Two of such types which are related directly to radio aspects of transmission are briefly discussed below.
The first type of such protection is related to protection against hardware failure. This protection is currently performed by means of a method known as Hot Stand-By configuration. Hot Stand-By protection is based on the presence of a spare transceiver that is put into operation when the main transceiver is subject to a hardware failure. In such case, the traffic is switched from the main transceiver to the spare transceiver.
The second type of protection is related to propagation effects such as effects caused by rain, fog, selective fading and the like. This type of protection is currently performed by means of frequency diversity or space diversity or the like.